1. Field of the Invention
The present invention relates to a wiring structure used in a semiconductor device and the like represented by an LSI, and more particularly, to a wiring structure applying a linear structure using a carbon element as a wiring material which possesses a minuteness, a high electrical conduction characteristic and a high allowable current density characteristic, and a method of forming the same.
2. Description of the Related Art
Recently, an LSI market led by a multi media field such as, in particular, a game machine, a portable terminal and the like tends to expand steadily. Regarding a wiring used in the LSI, the use of a copper (Cu) wiring which is conventionally in wide use is considered to reach limits in terms of resistance or current density in the future.
Accordingly, as an alternative to the copper (Cu) wiring, a linear structure made of a carbon element possessing a low-resistance and a resistance to a high current density is attracting attention. For the linear structure, a so-called carbon nano tube (CNT), a carbon nano fiber (CNF) or the like can be cited, which are attracting attention because of their many appealing physical properties.
Conventionally, some suggestions have been made to use the CNTs for the LSI wiring, and, for example, a research is being actively conducted to apply a CNT bundle to a via connection in a vertical direction (refer to Non-Patent Document 1). However, in the LSI wiring, it is naturally demanded to apply the CNTs not only to the via connection in the vertical direction but also to a wiring in a lateral direction. As a method of forming the CNT bundle as the wiring in the lateral direction, there is reported a technique of forming the CNT bundle in the lateral direction using so-called contact blocks being block-shaped base conductors (refer to Non-Patent Document 2). Catalytic metals necessary for forming the CNTs are formed on side surfaces of the contact blocks, and with the use of a CVD method, the CNT bundle is grown. Accordingly, the CNT bundle can be formed in a vertical direction with respect to the side surfaces of the contact blocks. By selecting the surface on which the CNT bundle is formed, that is, the surface on which the catalytic metal is formed, it is possible to select a growth direction of the CNT bundle.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2006-148063
[Non-Patent Document 1] IEEE International Interconnect Technology Conference 2006, pp. 230.
[Non-Patent Document 2] IEEE International Interconnect Technology Conference 2005, pp. 234.
[Non-Patent Document 3] Jpn. J. Appl. Phys. Vol. 41 (2002) pp. 4370-4374
When forming a wiring in the lateral direction according to a method of Non-Patent Document 2, it is necessary to connect a tip portion side of the CNT bundle to another wiring (or an electrode). Accordingly, for example, the CNT bundle is grown from the contact block, and thereafter, another contact block is formed afterward at the tip portion of the CNT bundle, as proposed in Non-Patent Document 3. However, there is generated a need for forming the contact blocks separately in a plurality of times in a wiring layer of the same hierarchy, which complicates a manufacturing process and increases cost, which is disadvantageous.
Further, Patent Document 1 discloses a method of forming the CNT bundle using a sidewall of an insulating film groove or using a thin partition conductive film, but, in this case, it is impossible to form a three-dimensional wiring network.
Furthermore, although it is indicated that the wiring network is built three-dimensionally using the copper (Cu) wiring as a foundation, there is a difference in an allowable current density between the CNT and the copper (Cu)(CNT: 109A/cm2, Cu: 106A/cm2), so that the combination of the CNT and the copper (Cu) may occur a wire breakage of the copper (Cu) wiring due to an electromigration. Further, the copper (Cu) is hard to be processed by a dry etching and the like, and thus the block formation is difficult.